Database Management Systems (dbms)

Components of a Database System

• Data

The data in the database integrated and shared.

• Hardware

Physically stores data, it can be secondary storage on which the database physically resides together with associated I/O devices.

• Software

Between the physical database & the users is a layer of software which is known as the DBMS.

• Procedures

Refer to the instructions & rules that governs the design & use of the database.

• Users

Application Programmers.

End-users

Controlling & Maintaining a Database

Database Administrator (DBA)

Database

Duties of the Database Administrator

• Installing and upgrades of database software
• Performance tuning
• Backup and recovery strategies
• Start the database & shutdown the database
• Monitoring the database
• Give and drop database access to the users
• Consultation with developers

Database Architecture

Data-bases

The Need of a Database Architecture

• Users need to access same data but in different customized views.
• User views can be changed without affecting data or other user views.
• Users are not deal directly with physical data storage
• Database administrator should be able to change the database storage without affecting the user’s views.

Database Architecture

An architecture for a database system is useful for explaining the structure of a specific database system

The database architecture is a three level architecture which reflects the underlying database system

Schemas and Instances

Database schema

• The description of a database called database schema
• The logical structure of the database
• Schema is defined during the database designing and is not frequently changed